ASO (AntiStreptolysin O) is an antibody directed against streptolysin O which is an exotoxin secreted by Streptococcus pyogenes. The assay is mainly used for the diagnosis of post-streptococcal complications (AAR, nephropathy, etc.), False positives may be observed in cases of hyperlipemic serum, or liver disease. The objective of our work is to evaluate the analytical performance of the ASO assay on the Abbott Alinity ci® at the Biochemistry laboratory of the Mohammed VI University Hospital in Oujda. The methodology of this work is based on the evaluation of reproducibility and repeatability, based on the technical accreditation guide (SH GTA 04) of the French Accreditation Committee (COFRAC). The results obtained for the different ASO dosage verification criteria show satisfactory repeatability for both levels (1: low / 2: medium), Intra-laboratory reproducibility was also satisfactory for both levels. By comparing these results with the CV used by the CLSI, we see that the results are consistent with and below the tolerated limits. This study shows that the Biochemistry laboratory of the Mohammed VI University Hospital in Oujda is able to provide accurate and precise results which regards with the requirements of learned societies for the determination of ASO.